Various disposable undergarments are commercially available today from various manufacturers for use by adults having problems with incontinence. Examples of such products are men's and women's briefs sold under the trademark Depend® by Kimberly-Clark Corporation. The Depend® products utilize a chassis mounting an absorbent core in the crotch region of the chassis. The chassis itself comprises a colored nonwoven with approximately fifty seven transversely extending strands of white spandex elastic threads laminated between layers of a nonwoven spunbond fabric to impart elasticity to hold the undergarment close to the body of the wearer. The spacing between the elastic fibers is relatively large, e.g., 6-7 mm, so that the chassis exhibits a somewhat puckered appearance.
Other manufacturers provide similar types of undergarments making use of chassis for holding an absorbent core, wherein the chassis includes a plurality of transversely extending elastic threads or filaments to render the undergarment close-fitting in the interest of concealability and wearer comfort. For example, Proctor & Gamble offers incontinence underwear under the trademark Always®. That product also makes use of a chassis comprising approximately fifty seven transversely extending and relatively widely spaced strands of white spandex elastic threads sandwiched between two layers of a nonwoven spunbond fabric. The chassis mounts an absorbent core and includes six additional colored elastic threads in the rear of the chassis to serve as an indicator of the back side of the product. Like the Depend® products the Always® products also exhibit a somewhat puckered appearance.
Livedo, USA offers an incontinent brief under the trademark LivDry™ That product makes use of a chassis having approximately forty widely spaced transversely extending white spandex elastic strands in panels laminated between two layers of white spunbond fabric, plus an additional eight colored elastic spandex strands in the rear of the product to serve as an indicator of the back side of the product. Like the Depend® products and the Always® products, the LivDry™ products also exhibit a somewhat puckered appearance.
Kimberly-Clark manufactures two other adult incontinence products under the names: Depend Silhouette and Depend Real Fit. Both products employ an elastic meltblown film fabric-like material that is difficult to process, has higher cost and has limited stretch.
Moreover, many current adult disposable absorbent products, utilize what is known as a fiberized bleached wood fluff pulp and a SAP (Super Absorbent Polymer) mixture for the absorbent core. At low ratios of 30% or less SAP to pulp ratio, the core mixture may or may not be wrapped in an absorbent tissue to prevent the SAP from falling apart or out of the core. At higher levels of SAP at 50% or more, the core must be wrapped to prevent the loose SAP from being shaken out. Also a core adhesive may be added to prevent the heavier SAP particles from being separated from the fluff pulp fibers. The pulp fiber in these products is required to rapidly manage the body fluid exudates until the SAP can desorb the fluff fibers to prepare the fluff fibers for the next exudates. For an adult the amount of exudate is can easily exceed 300 ml. or more delivered over a time period of more than 70 seconds at a rate similar or less than what infants void.
A significant problem with the current absorbent products that contain wood fluff pulp or even wrapped with a tissue or air-laid is in all cases their construction results in a core which feels wet against the body after it has received the voided fluid(s). To address this wet feel, almost all current absorbent product designs employ a distancing layer of synthetic fibers on top of the “wet core” as an attempt to create a “feel drier” layer. This synthetic distancing layer is often called a “fluid transfer layer”, “fluid acquisition layer”, or “acquisition distribution layer (ADL)” and is typically much smaller than the core that it covers, leaving the edges of the core exposed. Moreover, despite their design goal, such fluid acquisition layers only work to a limited degree. In this regard as the exudate leaves the body at 98 degrees Fahrenheit it quickly drops to about 90 degrees Fahrenheit as it enters the core of the absorbent product. This creates a cooling effect when touched by the skin, which may increase during the time worn. If left on for an extended period of time, the wet product will achieve a thermal equilibrium and equilibrate somewhere between room temperature and about 90 degrees Fahrenheit, depending upon ambient temperature and clothes worn. This difference can be further exacerbated depending upon the thermal conductivity of the materials chosen to absorb the exudate. But in all cases current wood pulp fluff absorbent products will feel wet and/or cold to the skin the longer the product is worn.
The current state of the art product design for the synthetic absorbent cores is based upon a synthetic continuous fiber matrix inter-layered with SAP. For example a polypropylene tow fiber similar to tow used in cigarette filter making was chosen. This material is purchased in a continuous form and is pulled out of the box and proceeds into an air trumpet or similar device or the like, to expand the fiber tow matrix. Then SAP particles are intermixed, adhesive is sprayed into the fiber SAP matrix and the entire matrix is wrapped to result in what is the state of the art of current so-called “pulp-less” core technology. This type of core has the major limitations of a slow absorbency rate. That rate is highly dependent upon the SAP chosen and on the adhesive type and amount required to attach the SAP to the tow fiber matrix. For example, if enough adhesive is provided to ensure that the SAP remains in its desired location within the core, that adhesive may limit the SAP's absorbent swelling due to coating part of the SAP particles. If less adhesive is utilized, while it may permit greater swelling and absorption of the exudate by the SAP, it may allow the SAP particles to fall from their positions in the core to the bottom of the crotch area, rendering it heavier and wetter in the crotch area when voided into and less absorbents at the ends.
Another example of current pulp-less core technology is gluing the SAP to the back sheet or inside the top or body facing sheet. This bonding process may limit the SAP from being fully expanded and utilized in absorbing the exudate. When bonded in such a matter, the SAP may also be applied in continuous rows to provide space for the fluid to travel unhindered. Or the SAP may be intermixed with ground wood pulp fibers of similar size to enhanced fluid movement in this inefficient design.
Current SAP limitations require having to choose between a higher absorbent capacity, with the disadvantage of having slower speed, or a faster SAP with less absorbing capacity. If the current SAPs are mixed, the fast acting SAP will very rapidly swell and may “gel-block” the slower acting, but higher absorption capacity SAP. If gel-blocking occurs, it will limit, or even prevent, the higher capacity SAP from desorbing the faster but lower capacity SAP.
In the past a cellulose acetate fiber core with a single SAP has been developed and commercially available, as has a non-SAP version. Current polypropylene filament tow technology has also been used for the absorbent cores. In this regard, such polypropylene tow cores used in the market today make use of round or oval homo-polymer polypropylene fibers, which provide minimal resistance to fluid flow through the SAP/tow fiber matrix, thereby only providing minimal dwell time for the fluid to be absorbed by the SAP.
While the aforementioned prior art products are generally suitable for their intended purposes, they nevertheless leave something to be desired from the standpoint their ability to absorb voided liquids quickly, easily and effectively without leakage, in an undergarment which is comfortable, thin, aesthetically pleasing and highly concealable under outer clothing. Thus, a need exists for disposable undergarments that address those needs.
The subject invention addresses those needs by providing an absorbent core assembly (also referred to hereinafter as a “composite absorbent core”) and a chassis for an undergarment, e.g., an adult brief, which overcomes the disadvantages of the prior art. The absorbent core assembly exhibits the ability to absorb voided liquids quickly, easily and effectively without leakage, and mounts the same within a chassis that is comfortable, thin, aesthetically pleasing and highly concealable under outer clothing. In particular, the chassis includes a much larger number of transversely extending elastic strands, which are spaced closer to one another to provide a significantly improved fit to the wearers body, while at the same time providing a flatter appearance than the puckered look of the prior art incontinent undergarments. The absorbent core assembly is composed of two sections of SAP for quickly and securely absorbing voided liquid without leakage. One section of the core, which is located facing the wearer's body, includes a plurality of pockets partially filled with a free, slow acting, but highly absorbent SAP. The other section of the core is located facing away from the wearer's body and includes a plurality of pockets partially filled with a free, fast acting, but lower absorbency SAP. With this construction, liquid voided into the core is initially quickly absorbed by the fast acting SAP section, whereupon the section with the slow acting, but high absorbency SAP desorbs the section with the fast acting SAP to securely contain the voided liquid therein and prevent any leakage out of the core.
The production of disposable absorbent products as presently accomplished also leaves much to be desired. In this connection, the most common process to produce absorbent disposable products with absorbent cores used today and for the past forty-five years is to start with bleached softwood wood pulp on rolls produced at a pulp mill. Forests of mature trees are harvested to supply pulp wood to these mega mills. Note that each mature tree can absorb approximately four tons of carbon dioxide per year. After harvesting mature trees, saplings are usually planted and take twenty to forty years to mature. Pulp mills are quite large, processing trees takes substantial energy, chemicals such as chlorine or chlorine dioxide are very toxic, but are required in the bleaching process. Pulp mills today usually cost between about one half and one billion dollars or more to construct. This limits the construction of new pulp mills. This also creates a very high incentive, by current manufacturers, not to move away from or abandon using such an existing large capital, land (trees) and labor investment.
These bleached absorbent pulp rolls are then shipped to the absorbent garment manufacturer, also known as a converter. The rolls of bleached wood pulp are subsequently processed through a fiberizing hammer mill on the production converting line to fiberize the bleached softwood absorbent pulp into discreet fibers. From the hammer mill these fibers are conveyed by air to either a continuous tissue layer on top of a screen like material with vacuum under said system or into a pocketed shaped screen on a rotating drum pulled into the pocket shape by vacuum. These hammer mills require high levels of energy to rotate the hammers at approximately ten thousand revolutions per minute, usually requiring 720-volt power supply limiting such equipment to heavy industrial power grid areas with a large voltage and amperage power supply. The hammer mills and subsequent supporting process also cost approximately one million dollars or more. Some processes used today have two such million-dollar hammer mills processes. In addition, these processes require substantial amounts of compressed air, vacuum and an extensive air filtration system to filter out substantial amounts of dust. This is required for both a single absorbent product converting machine and the entire factory. If it contains more than one such machine, substantially more equipment is required. All adding to the cost of the million-dollar hammer mill systems. Because of the noise of these hammer mills operators are required to wear hearing protection to negate some of the noise. Hearing protection can also prevent operators from effectively communicating with each other, which may contribute to on the job accidents.
Since the 1980's such absorbent products converting systems added some amount of super absorbent polymer, commonly referred to as SAP. Chemically it is polymerized polyacrylic acid, partially neutralized with sodium hydroxide. Other additives may be added in the polymerization process or topically added during the drying process to enhance desired differences. This SAP material increases the total capacity of the absorbent system without adding additional fiberized wood pulp. The advantage of SAP is to assist in desorbing or pulling moisture away from the fiberized wood pulp to increase the dryness of such a system. The disadvantage of SAP is its slow absorbing properties that cause such absorbent systems to require fiberized wood pulp to manage fluid insult speed. In some cases, the SAP is further modified to increase absorbent speed, but this reduces absorbent capacity and results in the issue of gel blocking. Gel blocking is the problem of the outer SAP particles absorbing fluid, swelling and blocking or preventing the fluid from reaching the inner SAP particles. The SAP particles are also conveyed by air into the fiberized pulp stream to create the desired ratio of fiberized wood pulp to SAP (frequently referred to as the pulp/SAP ratio). With higher ratios above 30% or more, a tissue wrap maybe required. Whereas lower amounts of SAP or a ratio below 30% may not require a tissue wrap. Usually no additives or a slight amount of misted water or mineral oil and the like are added into the hammer mills to enhance processability. In some cases, a small amount of an absorbent core adhesive may be used to add integrity to the fluff/SAP absorbent core. This has the drawback of gumming up the process, so it has not been universally accepted and utilized in this type of construction.
Dual forming fluff pulp systems are used by some absorbent product manufacturers to overcome some of the above noted problems. In particular, some modifications of such existing pulp/SAP absorbent products production systems include using a dual or double fiberizing system. In such cases the absorbent core is composed of two layers, usually including SAP in both layers. This is to provide for marketing and advertising claiming “dual core.” There may be a small improvement in providing more consistency in the absorbent core if it incorporates two similar pulp/SAP ratios. In some situations, the manufacture of such absorbent cores may choose to use a different pulp in the body side layer than the away from body side layer. In some cases, this could be a highly crosslinked cellulose pulp “curly fibers” or like materials is usually found in the body side layer. And in some other situations, the manufacturer may choose to add a higher level of SAP in the body side layer to promote dryness, depending upon the away from the body layer to manage absorbency speed. This only increases dryness slightly, also known as “rewet” or wet back against the body. In this construction, total absorbency or absorbent capacity is dependent upon the total amount of SAP, fluff pulp and tissue, and their inherent absorption capacities, regardless of the construction.
In all cases referenced previously, these processes require a large, energy intensive, noisy fiberization system with immense vacuum and dust collection systems. As discussed previously, adding the cost of a least one million dollars or more for such systems for each drum former not only increases the total costs, but requires substantial hearing protection to protect both the machine operators and anyone else in said factory from hearing damage due to the loud sound of running hammer mills and their supporting air handling systems. In all situations referenced, the absorbent product contains fiberized wood pulp to manage the speed of the absorbent insult from the wearer's body. A usual body void is about 150 to 250 ml over about 70 to 90 seconds. The SAP by itself does not adequately absorb fluid at such a fast rate. Thus, fiberized fluff pulp is required to manage the initial speed. Other alternative absorbent cores and processes have been proposed. One such approach in an attempt to improve absorbent core thinness, SAP containing Airlaid absorbent cores have been created. An Airlaid absorbent is constructed of fiberized wood pulp that is usually mixed with up to 70% SAP and either adhesively bonded or thermally bonded and compressed into a thick paper like material. Airlaids without SAP are sold as high-end or expensive disposable paper napkins or the like. While such absorbent cores have a greater thinness than pulp/SAP absorbent cores, they necessarily have a slower absorbent speed and reduced total capacity per gram of Airlaid due to the bonding under pressure to make the absorbent core thinner. Moreover, cost is increased for this type of approach due to the energy required to thermally secure or glue this construct together. Cost also increases as Airlaid cores are usually created at a different facility and shipped to the converting facility. The deficiency in absorption speed has delayed introduction of such products into any markets. There have been hybrid products seen with single layers of Airlaid materials on top of or underneath a standard pulp/SAP absorbent core to provide a marketing point of difference.
Another alternative absorbent core produced from about 2003 to 2005 has been an absorbent core composed of cellulose acetate fibers with free SAP mixed in and wrapped with a heavier weight tissue. The advantage of such an absorbent core is comfort as it will not be as insulating and warm as a product manufactured containing cellulose fluff pulp. The disadvantage is absorbency rate and speed. Such a system is not as fast as required to handle a full absorbent void from infants or adults. A product sold using this construct was Parent's Choice Protective Underwear sold by Walmart, Inc. from approximately 2003 to 2005. It was an adequate product for a child pull up that is meant to be used only once as it was a toilet training absorbent back up product for slight accidents. This product was known to have the desired reduced thermal insulating properties compared to a fiberized cellulosic containing product. Children, who were well known for removing typical pulp based pull-up like absorbent garments, due to being uncomfortably warm to the body, did not remove these products. Another variant of this product was a baby diaper seen in the Middle-East produced by RK Beaufort and incorporated polypropylene filaments in place of the cellulose acetate fibers to reduce cost. Due to the high compressibility of these products compared to standard fiberized wood pulp/SAP, these products were desirable due to the lower cost of transportation. However, their absorbency rate is highly determined by SAP absorption speed and the SAP used in these constructs have a vortex time of over sixty seconds, rendering them unsuitable to hold a rapid normal body void. Therefore, these baby diapers relied on tight gasketing abound the body to hold the free liquid within the diaper until the SAP could begin to swell and absorb the liquid.
Other variants to design absorbent cores include incorporating a SAP containing foam. These cores, however, are unacceptable for urine usage as foam, when wet, will lose structural integrity.
Foam/SAP products have been successfully utilized for menstrual pads, as the menstrual flow is usually approximately 5 grams or so, not the 250 to 500 grams or more of urine usually required for an infant or adult incontinent absorbing product.
Another approach to constructing an absorbent core includes a system developed by Migaku Suzuki, Ph.D., of the Japan Absorbent Technology Institute (known as JATI). In that construction, Dr. Suzuki ground the pulp much finer than is created by a hammer mill, which fiberizes sheets of wood pulp. With similar particle size when compared to SAP particles, both sets of particles are glued to a back sheet or other material. This creates an extremely thin absorbent core. However, the resulting absorbent core is still unable to manage the speed of an absorbent insult due to the slowness of the SAP and predicated upon the speed of the glue to delaminate from the SAP particles. Moreover, cost is dramatically increased with the addition of an adhesive and the secondary processing required to grind the wood pulp into a smaller size.
Due to the above mentioned environmental impact issues, hearing safety, high capital costs have prevented new manufacturers from entering the absorbent products arena. Also, due to the large investments, legacy contracts, processes, equipment invested, current manufacturers have been resistant to move away from their existing established processes. This has been the scenario for the past forty-five years.
Thus, a need also exists for methods for producing absorbent disposable garments and/or composite absorbent cores which overcomes the disadvantages of the prior art. The subject invention addresses that need by providing methods of making undergarments and composite absorbent cores for use in undergarments, which overcomes the disadvantages of the prior art.